1. Field of the Invention
This invention generally relates to the machine tool art and more particularly to an improved fixture for accurately holding a workpiece that is to be machined.
2. Description of the Prior Art
In the past, tubular members such as externally threaded couplings for coaxially arranged pipes or tubes have been machined by placing the coupling on a mandrel and then bringing the thread cutting means into engagement with the peripheral surface of the coupling. Because the workpiece must be rapidly loaded onto the mandrel and unloaded from the mandrel, it is evident that there must be a relatively loose fit between the external surface of the mandrel and the internal surface of the workpiece.
This loose fit has, in the past, caused some difficulties in the machining of the workpiece and has caused some reduction in the accuracy of the machining operation.